Barium abundance

Fig. 8.6. Relative abundances of heavy nuclei in a halo star. Abundances are normalised to the barium abundance. The continuous line represents r abundances (from Kappeler). The excellent agreement suggests that previous nucleosynthesis was dominated by the r process and that the star CS 22892-052 formed from the debris of a type 11 supernova. (From Sneden 2001.)...

The reaction is used for the chain extension of aldoses in the synthesis of new or unusual sugars In this case the starting material l arabinose is an abundant natural product and possesses the correct configurations at its three chirality centers for elaboration to the relatively rare l enantiomers of glucose and mannose After cyanohydrin formation the cyano groups are converted to aldehyde functions by hydrogenation m aqueous solution Under these conditions —C=N is reduced to —CH=NH and hydrolyzes rapidly to —CH=0 Use of a poisoned palladium on barium sulfate catalyst prevents further reduction to the alditols... 

Zirconium occurs naturally as a siUcate in zircon [1490-68-2] the oxide baddeleyite [12036-23-6] and in other oxide compounds. Zircon is an almost ubiquitous mineral, occurring ia granular limestone, gneiss, syenite, granite, sandstone, and many other minerals, albeit in small proportion, so that zircon is widely distributed in the earth s cmst. The average concentration of zirconium ia the earth s cmst is estimated at 220 ppm, about the same abundance as barium (250 ppm) and chromium (200 ppm) (2). 

Calcium [7440-70-2J, Ca, a member of Group 2 (IIA) of the Periodic Table between magnesium and strontium, is classified, together with barium and strontium, as an alkaline-earth metal and is the lightest of the three. Calcium metal does not occur free in nature however, in the form of numerous compounds, it is the fifth most abundant element constituting 3.63% of the earth s cmst. 

Most abundant group of materials, composed of silicates of aluminium with sodium, potassium, calcium, and rarely barium. Most economically important mineral. Used for ceramics, glass, abrasive wheels, cements, insulation and fertilizer. 

Barium (eighteenth most abundant element) is also rather rare it occurs as the mineral barite, BaSCV... 

On the other hand, if the feed gas contains H20 and/or C02 the most abundant barium species involved in the storage process are Ba(OH)2 and/or BaC03, respectively. These aspects will be discussed and clarified in the following sections. 

Abstract. [La/Eu] and [Ba/Eu] for a sample of Barium stars were determined in order to evaluate the ratio of abundances of s- and r-elements. The results have been compared to previous work dealing with normal red giants and dwarfs with metallicities in the range -3 < [Fe/H] < +0.3. 

Ba (La) and Eu abundances have a linear relation for stars whose metallicities are below -2.75. At higher metallicities the relation is still linear, but the fit shows different slope. Since Barium stars are rich in s-elements, that relation is different relative to normal stars with similar metallicities. 

In the other study. X-ray fluorescence spectroscopy was used to analyze trace element concentrations by observing dusts on 37 ram diameter cellulose acetate filters (20). Twenty-three elutriator and twenty-three area samples from 10 different bales of cotton were analyzed. The average fraction of total dust accounted for by the elements analyzed was 14.4% amd 7.6% for vertical elutriator and area samples, respectively. Although the variation in absolute quantity of atn element was high, the relative abundance of an element was consistent for measurements within a bale. Averaged over all the samples analyzed, calcium was the most abundant element detected (3.6%), followed by silicon (2.9%), potassium (2.7%), iron (1.1%), aluminum (1.1%), sulfur (1.0%), chlorine (0.8%) and phosphorous (0.6%). Other elements detected in smaller aunounts included titanium, manganese, nickel, copper, zinc, bromine, rubidium, strontium, barium, mercury amd lead. 

Barium is the 17th most abundant element in the Earth s crust, making up about 0.05% of the crust. It is found in the minerals witherite, which is barium carbonate (BaCO ), and barite, known as barium siflfate (BaSO ). Pure barium metal does not exist on Earth—only as compounds or in minerals and ores. Barium ores are found in Missouri, Arkansas, Georgia, Kentucky, Nevada, California, Canada, and Mexico. 

Beyond iron lies a first population of so-called s-process nuclei, which includes among others barium and lead. This population has an abundance distribution with peaks around mass numbers 87, 138 and 208. These nuclei are produced by slow neutron capture, referred to as the s process. A second population, slightly shifted from the first, including gold, platinum and uranium, is imputed to the process of rapid neutron capture, referred to as the r process. 

British chemist Sir Humphry Davy Soft, reactive, abundant metal as barium sulfate, it blocks transmission during diagnostic X rays to highlight organs and other tissue. 

Barium was discovered in 1808 by Sir Humphrey Davy. Its abundance in the earth s crust is about 0.0425% (425 mg/kg). The element also is found in sea water at trace concentration, 13 J,g/L. It occurs in the minerals barite or heavy spar (as sulfate) and witherite (as carbonate). 

Strontium is found in small quantities in many rocks and soils, mostly associated with calcium and barium. Its abundance in the earth s crust is about 370 mg/kg, about the same as barium. The average concentration of this metal in sea water is about 7.9 mg/L. 

Totaling 84, these elements include, in descending order of abundance, titanium, hydrogen, phosphoms, nitrogen, barium, and strontium, each one of them in less than one percent. 

Nickel and vanadium are the most abundant metals found in crude oil. Other metals, metalloids, and nonmetals including aluminum, arsenic, barium, calcium,... 

The abundances of krypton and xenon are determined exclusively from nucleosynthesis theory. They can be interpolated from the abundances of neighboring elements based on the observation that abundances of odd-mass-number nuclides vary smoothly with increasing mass numbers (Suess and Urey, 1956). The regular behavior of the s-process also provides a constraint (see Chapter 3). In a mature -process, the relative abundances of the stable nuclides are governed by the inverse of their neutron-capture cross-sections. Isotopes with large cross-sections have low abundance because they are easily destroyed, while the abundances of those with small cross-sections build up. Thus, one can estimate the abundances of krypton and xenon from the abundances of. v-only isotopes of neighboring elements (selenium, bromine, rubidium and strontium for krypton tellurium, iodine, cesium, and barium for xenon). 

Strontium has four naturally occurring isotopes (Table 4.2). It is a member of the alkaline earths (Group 2A) along with beryllium, magnesium, calcium, barium, and radium (Fig. 2.4). Strontium substitutes for calcium and is abundant in minerals such as plagioclase, apatite, and calcium carbonate. 

STRONTIUM.—Although less abundantly diffused, it resembles barium both in ita chemical and geological relations. Like it strontium is neveT found native, hut only as carbonate and sulphate. It was first recognized by Hope in 1792, in the mineral sirontiantte, so called from Strontian in Scotland. 

Hydrogen sulphide is present in many mineral springs, and even free sulphur is occasionally found therein.2 Many metallic sulphides, for example, iron pyrites, galena, zinc blende, stibnitc and cinnabar, occur abundantly. Sulphur dioxide, sulphites, sulphuric acid and sulphates are also found in nature, more especially in waters springing from volcanic earth, whilst the sulphates of certain metals such as calcium, barium and magnesium exist in large deposits. 

Sulphates occur abundantly in nature, the chief being those of calcium, barium, strontium, magnesium, aluminium, iron, zinc, copper, sodium and potassium. 

At very high temperatures the sulphates of metals such as copper, zinc, iron, aluminium and chromium tend to lose sulphur trioxide (largely in the form of sulphur dioxide and oxygen) and to give residues of the corresponding oxides.7 Calcium sulphate is stable up to 1300° C., above which temperature it melts and immediately undergoes almost complete decomposition with abundant evolution of fumes.8 Very slight decomposition has been observed with barium sulphate at 1300° C.9... 

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